public void CreateRequestContentString_Test()
        {
            var expectedMessage = @"GET http://test.com:2020/
Accept-Encoding: gzip
Content-Type: application/json
Content-Length:  11

hello world
";
            var request         = new HttpRequestMessage(HttpMethod.Get, "http://test.com:2020");

            request.Content = new StringContent("hello world");
            request.Headers.AcceptEncoding.Add(new StringWithQualityHeaderValue("gzip"));
            request.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");

            var requestStr = BatchRequest.CreateRequestContentString(request).Result;

            Assert.AreEqual(expectedMessage, requestStr);
        }